BULLA

(Lat.) A stud or bo , but more particularly an ornament in the shape of a heart, worn round the neck by noble Roman children till they were seventeen years old; when they a umed the manly dre of the toga, and suspended the bulla as a consecrated offering to the lares or household gods. Bu'lla. (Lat. bulla, a bubble.) A genus of Acerous Gastropodous Mollusks, the shell of which is more or le globose, or inflated like a bubble; having no visible or projecting spire, which is concealed by the large external whorl, which is elevated above the rest. The columella makes a convex prominence, which gives a crescentic form to the aperture of the shell; the animal breathes by gills, but has no respiratory tube or siphon, and consequently the margin of the aperture of the shell is entire, or without a fi ure or canal. All the species of bulla are remarkable for a shelly apparatus of three pieces which converts the stomach into a gizzard or triturating cavity. These gastric calcareous pieces have been described as a bivalve shell of a new genus. [s. 185]